1. Field of the Invention
The present invention relates to an image processing apparatus installed on a vehicle and is designed to take an image of a forward view of the vehicle.
2. Description of Related Art
Image processing apparatuses which are installed on vehicles have been developed. Such apparatuses can be applied to automatic driving techniques. As for an image processing apparatus, the following three characteristics are required.
Firstly, in order to recognize the lane on which the vehicle travels, it is necessary to take an image of the front view of the vehicle by a camera such as the CCD (Charge Coupled Device) or the CMOS (Complementary Metal Oxide Semiconductor) image sensor and perform processing of the image in real time.
Secondly, a correct recognition of the lane is required for the safe driving. Therefore, the input image data of the lane is required to have a feature that brings about less error in the image recognition.
Thirdly, it is required to extract information of edges of the lane marking drawn on the surface of the lane in the front view image. In such information, the position of a lane division line on the lane surface, the existence or absence of a branch of a lane, or the existence or absence of a dead end or an obstacle is represented, for example.
Here, some examples of image processing apparatuses for vehicles are introduced.
Japanese Laid Open Patent Application JP-P 2003-308534A describes a white line recognition apparatus. In this white line recognition apparatus, a forward road surface image including a running lane is imaged, and the road surface image is laterally scanned. By detecting an up-edge where the intensity (namely, brightness, concentration or value of a pixel) of the image is relatively increased by more than a predetermined value and a down-edge where the intensity of the image is relatively decreased by more than a predetermined value, a bright portion caused by a white line on a road surface is extracted. At this time, white line position candidate points which represent side edge portion of the lane is determined for each longitudinal position of the road image. In this case, when only one pair edge composed of an up-edge and a down-edge that correspond to the bright portion is detected at the same position in the longitudinal direction of the road surface image, a point having a predetermined relative position preset for the pair edge is defined as the white line position candidate point. Also, when a plurality of pair edges are detected, in accordance with the array of the plurality of pair edges, a point having a predetermined relative position preset for the plurality of pair edges is defined as the white line position candidate point. In this way, in the white line recognition apparatus, even in the road portion in which the plurality of white lines are arrayed, a white line position candidate point when the white line of the road portion is assumed to be the single road portion is obtained.
Also, Japanese Patent Publication No. 2712809 describes a vehicle obstacle detection apparatus. In this vehicle obstacle detection apparatus, only a horizontal edge and a vertical edge which extend longer as they exist in the lower portion of a screen from an input image are extracted, and an area surrounded by the horizontal and vertical edges are recognized as an obstacle. In this construction, a distance measuring system can be constructed by using only one camera.